TEXAS WASTEWATER A QUESTIONS
AND ANSWERS (GRADED A+)
Describe proper design of force main wastewater lines. - ANSWER-Minimum two fps
velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
Describe proper design of gravity wastewater lines. - ANSWER-Designed to flow half
full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
What is the effective chlorine disinfecting agent? - ANSWER-Hypochlorous Acid (HOCl)
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir
is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow
channel is 3 feet deep. a. What is the detention time in hours? - ANSWER-5.08. hrs
What activated process cannot nitrify in a single stage? - ANSWER-Contact
Stabilization
What is the GPM output of a piston pump with an 8-inch diameter piston with a 10-inch
stroke operating at 50 strokes per minute? - ANSWER-108.8 gpm
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir
is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow
channel is 3 feet deep.
What is the surface loading in gal/ft2/day?
What is the weir loading in gal linear ft/day? - ANSWER-353.68 gallons & 5684.11
A primary clarifier has a flow of 3.0 MGD and has a diameter of 100 feet. It is 12 feet
deep and has 24 inches of freeboard. What is the detention time in hours? - ANSWER-
4.7 hrs
Anaerobic digester gas should contain? - ANSWER-65-75% methane, 25-35% carbon
dioxide and 1-5% nitrogen.
An activated sludge plant has an average daily flow of 3.5 MG. The aeration tank
capacity is 1.2 MG with a MLSS concentration of 3200 mg/L. The clarifier has a capacity
of 400,000 gallons with a MLSS concentration of 6,000 mg/L. The wasting rate is
40,000 gallons per day with a MLSS concentration of 8, 000 mg/L. The effluent TSS is
18 mg/L. Assuming volatile concentrations of 70%, what is the MCRT and what type of
activated sludge plant should this be? - ANSWER-16.29 Days
, What are some of the causes of filaments in the aeration basin? - ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
When an RBC is operating correctly, how will the slime appear on the media? -
ANSWER-Grey to brown 0.05 to 0.1 inches thick
What activated sludge process does not achieve complete nitrification? - ANSWER-
Contact Stabilization
In the selection of forced main wastewater piping, what is the minimum working
pressure? - ANSWER-150 psi
The oxygen depletion of BOD dilution water should not exceed - ANSWER-0.2 mg/L.
What is the minimum air gap when making water and wastewater connections? -
ANSWER-Minimum of one inch or twice the inlet pipe size whichever is greater.
An anaerobic digester must maintain an average year round temperature of - ANSWER-
95 degrees F.
Which of the following methods would you use to increase the degree of nitrification in
an activated sludge plant? - ANSWER-increase dissolved oxygen levels and increase
the sludge age
A 30-inch diameter wastewater interceptor is observed to be flowing half-full at about
two fps. The approximate volume of wastewater flowing through the pipe is ________. -
ANSWER-The approximate volume of wastewater flowing through the pipe is about
4.91 cubic feet per second (cfs), or 2203.2 gallons per minute (GPM).
A one-cylinder reciprocating sludge pump with a 10-inch bore and a 5-inch stroke
pumps at a rate of 50 cycles per minute. How many minutes must the pump be
operated to pump 5,000 gallons of sludge? - ANSWER-58.82
Review exhibit E in the separate package. According to the DMR, the TSS data shows
________.
a. a violation of the daily average
b. a violation of the number of grab samples
c. a violation of the 7-day average
d. a violation of the daily max
e. no violation - ANSWER-Need DMR
AND ANSWERS (GRADED A+)
Describe proper design of force main wastewater lines. - ANSWER-Minimum two fps
velocity with the smallest pump operating alone. Minimum four inch diameter pipe with
150 psi rating.
Describe proper design of gravity wastewater lines. - ANSWER-Designed to flow half
full ,under normal conditions, at a minimum of two fps and a maximum of ten fps.
What is the effective chlorine disinfecting agent? - ANSWER-Hypochlorous Acid (HOCl)
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir
is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow
channel is 3 feet deep. a. What is the detention time in hours? - ANSWER-5.08. hrs
What activated process cannot nitrify in a single stage? - ANSWER-Contact
Stabilization
What is the GPM output of a piston pump with an 8-inch diameter piston with a 10-inch
stroke operating at 50 strokes per minute? - ANSWER-108.8 gpm
A treatment plant has a clarifier that is 60 feet in diameter and is 10 feet deep. The weir
is 2 feet inside the outer clarifier wall. The flow is 1.0 MGD. The weir and outflow
channel is 3 feet deep.
What is the surface loading in gal/ft2/day?
What is the weir loading in gal linear ft/day? - ANSWER-353.68 gallons & 5684.11
A primary clarifier has a flow of 3.0 MGD and has a diameter of 100 feet. It is 12 feet
deep and has 24 inches of freeboard. What is the detention time in hours? - ANSWER-
4.7 hrs
Anaerobic digester gas should contain? - ANSWER-65-75% methane, 25-35% carbon
dioxide and 1-5% nitrogen.
An activated sludge plant has an average daily flow of 3.5 MG. The aeration tank
capacity is 1.2 MG with a MLSS concentration of 3200 mg/L. The clarifier has a capacity
of 400,000 gallons with a MLSS concentration of 6,000 mg/L. The wasting rate is
40,000 gallons per day with a MLSS concentration of 8, 000 mg/L. The effluent TSS is
18 mg/L. Assuming volatile concentrations of 70%, what is the MCRT and what type of
activated sludge plant should this be? - ANSWER-16.29 Days
, What are some of the causes of filaments in the aeration basin? - ANSWER-a. low DO
b. low organic loading
c. septic wastes
d. nutrient deficiencies .
e. high sulfur content
When an RBC is operating correctly, how will the slime appear on the media? -
ANSWER-Grey to brown 0.05 to 0.1 inches thick
What activated sludge process does not achieve complete nitrification? - ANSWER-
Contact Stabilization
In the selection of forced main wastewater piping, what is the minimum working
pressure? - ANSWER-150 psi
The oxygen depletion of BOD dilution water should not exceed - ANSWER-0.2 mg/L.
What is the minimum air gap when making water and wastewater connections? -
ANSWER-Minimum of one inch or twice the inlet pipe size whichever is greater.
An anaerobic digester must maintain an average year round temperature of - ANSWER-
95 degrees F.
Which of the following methods would you use to increase the degree of nitrification in
an activated sludge plant? - ANSWER-increase dissolved oxygen levels and increase
the sludge age
A 30-inch diameter wastewater interceptor is observed to be flowing half-full at about
two fps. The approximate volume of wastewater flowing through the pipe is ________. -
ANSWER-The approximate volume of wastewater flowing through the pipe is about
4.91 cubic feet per second (cfs), or 2203.2 gallons per minute (GPM).
A one-cylinder reciprocating sludge pump with a 10-inch bore and a 5-inch stroke
pumps at a rate of 50 cycles per minute. How many minutes must the pump be
operated to pump 5,000 gallons of sludge? - ANSWER-58.82
Review exhibit E in the separate package. According to the DMR, the TSS data shows
________.
a. a violation of the daily average
b. a violation of the number of grab samples
c. a violation of the 7-day average
d. a violation of the daily max
e. no violation - ANSWER-Need DMR
